1. Field of the Invention
The present invention relates to a distributor-type fuel injection pump that uses an innercam system for supplying fuel to engines, including diesel engines, and specifically, to an fuel injection pump that employs a method in which plungers make a reciprocal movement in relation to a rotating member that rotates synchronously with the engine in the direction of the radius of the aforementioned rotating member.
2. Description of the Related Art
Distributor-type fuel injection pumps using the innercam system in the known art include the one disclosed in Japanese Unexamined Patent Publication No. S57-179362. In this fuel injection pump, a cam ring 54 is provided on the circumference of a rotor 20 (rotating member) concentrically, pistons 40 (plungers) are provided on the cam surface formed on the inside of the cam ring 54 via rollers 56 and roller shoes 58. The pistons 40 make a reciprocal movement in the direction of the radius of the rotor 20. During the intake process, in which the pistons 40 move toward the outside in the direction of the radius, fuel is taken into the compression space via an intake passage 34. During the force feed process, in which the piston moves toward the inside in the direction of the radius, the fuel which has been pressurized in the compression space is sent out via a fuel distribution passage. Then, during the force feed process, when the fuel is cut off from an overflow passage 62, the injection ends. The force feed timing is adjusted by linking a timing mechanism 60 (timer mechanism) to the cam ring 54 and then by causing the cam ring 54 to turn in the direction of the circumference with the timing mechanism 60.
However, when the pressure in the compression space is raised in order to use the injection pump described above for a diesel engine or the like, a reaction force, which works on the cam ring via the pistons, the rollers and the roller shoes, also increases. This, in turn, increases the lead applied in the direction of the rotation of the cam ring. Because of this, when the lead applied in the direction of the rotation of the cam ring exceeds the force with which the cam ring is driven by the timer mechanism, accurate advance angle control can no longer be performed, notwithstanding the timer adjustment, resulting in inconsistent injection timing and unstable performance. In order to solve this problem, a timer mechanism with a drive force that can overcome the lead described earlier during fuel force feed is required. However, if such a timer mechanism is to be achieved in the conventional structure, in which the timer mechanism is connected to the cam ring, the timer mechanism becomes large and complicated.